Antiphospholipid antibodies, including beta-2 glycoprotein anitboides, are associated with excessive clotting. They interfere with the body's blood clotting process in a way that is not fully understood. (See the "What is being tested?" section for more.)

As beta-2 glycoprotein 1 antibody is less common than the other antiphospholipid antibodies, it may be ordered as a follow-up to those tests to provide a health practitioner with additional information. However, beta 2 glycoprotein 1 antibodies have been reported to be more specific (but less sensitive) than cardiolipin antibodies for the diagnosis of APS.

Laboratory tests can detect three different classes of these autoantibodies: IgG, IgM, and IgA. If all three of the initial antiphospholipid antibody tests for the IgG and IgM classes are negative but APS is still suspected, then the IgA class of these antibodies may be tested, along with other less common antiphospholipid antibodies, such as anti-phosphatidylserine and anti-prothrombin. However, the value of testing for the IgA class of antiphospholipid antibodies remains controversial. According to the international consensus statement on APS, the presence of the IgA class (either anticardiolipin antibodies or beta-2 glycoprotein 1 antibodies) does not fulfill laboratory criteria for APS diagnosis.

If a beta-2 glycoprotein 1 antibody is detected, the same test will be repeated about 12 weeks later to determine whether its presence is persistent or temporary. If a person with an autoimmune disorder tests negative for antiphospholipid antibodies, testing may be repeated at a later time to determine if the person has begun to produce antibodies, as they may develop at any time in the course of disease.

When is it ordered?

Beta-2 glycoprotein 1 antibody tests and other antiphospholipid antibody testing may be ordered when a person's symptoms suggest a blood clot in a vein or artery. Symptoms may include pain and swelling in the extremities, shortness of breath, and headaches.

Beta-2 glycoprotein 1 antibody tests may also be ordered when a woman has had recurrent miscarriages or when a person has signs and symptoms of antiphospholipid syndrome (APS), such as:

What does the test result mean?

A positive beta-2 glycoprotein 1 antibody test may indicate that the person has antiphospholipid syndrome (APS), as they are most frequently seen with the condition. Current diagnostic criteria for APS are based upon both clinical findings and the persistent presence of one or more antiphospholipid antibodies. If a high level of beta-2 glycoprotein 1 antibody is detected initially and then again 12 weeks later in a person with signs of APS, then it is likely that the person has the disorder. This is especially true if other antiphospholipid antibodies are also detected.

If a person is negative for beta-2 glycoprotein 1 antibodies but positive for other antiphospholipid antibodies and has signs and symptoms, then that person also likely has APS.

If the test is weakly to moderately positive for beta-2 glycoprotein 1 antibodies and weakly positive or negative for other antiphospholipid antibodies, then the antibody presence may be due to a condition other than APS. If subsequent testing is negative, then it is likely that the antibodies were temporary. This may be seen with an acute infection.

A single positive beta-2 glycoprotein 1 antibody result is not diagnostic of APS, and a negative result does not rule out antiphospholipid antibody development. They just indicate the presence or absence of the antibody at the time of testing. That is why a diagnosis of APS requires clinical symptoms plus at least two positive tests for an antiphospholipid antibody at least 12 weeks apart.

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This article was last reviewed on March 16, 2015. | This article was last modified on March 18, 2015.

The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.

The modified date indicates that one or more changes were made to the article. Such changes may or may not result from a full review of the article, so the two dates may not always agree.